A radio access network (RAN) refers to a network between mobile devices and a core network. In traditional wireless macro-cell networks, an area may be geographically divided into a plurality of cells and cell sectors, each served by a wireless base station communicating with a core network. The part of the RAN between the wireless base stations and the core network is referred to as the wireless backhaul. As the demand for high-speed wireless communications continues to increase, reaching the limits of macro cells in terms of the number of locations and penetration capability in indoor or densely-populated areas, research and industry are moving towards small-cell deployments with denser and smaller cells.
Wireless fronthaul and mobile fronthaul are emerging network segments that enable a centralized-RAN (C-RAN) architecture suitable for small-cell deployments. In a C-RAN architecture, the digital baseband (BB) processing that is typically performed at wireless base stations located at remote cell sites is relocated to centralized baseband units (BBUs) located at a central office (CO) or nearby a core network. As such, the wireless base stations located at remote cell sites are replaced by remote radio units (RRUs) that interface with antennas for wireless radio frequency (RF) transmissions and receptions with no or limited digital BB processing. Wireless fronthaul refers to the part of the RAN between the RRUs and the BBUs. By relocating the digital BB processing to the centralized BBUs, the C-RAN architecture may enable resource sharing and coordinated multipoint (CoMP) processing, such as joint signal processing, joint interference mitigation, and/or joint scheduling among multiple antennas in cells, thus improving network performance and efficiency. The C-RAN architecture may also support massive multiple-input multiple output (MIMO) for high-throughput wireless transmission.
Wireless fronthaul may be enabled by optical fiber communication technologies, where optical fiber links may be employed for transporting signals and/or data between the RRUs located at the remote cell sites and the BBUs located at the central site. Some advantages of optical fiber transmissions may include low power loss, low latency, and high bandwidths (BWs). However, the employments of optical fibers and optical hardware add cost to the wireless fronthaul network. Thus, efficient usage of optical fiber links and optical hardware may be important in wireless fronthaul design.